In today's automotive engine systems, there is an increased demand for low cost, direct injection. In common rail injection systems, the fuel is delivered by means of a high pressure pump from a fuel tank to a fuel rail which serves as a storage reservoir for the fuel. The fuel is under high pressure in the fuel rail and can be injected directly into the cylinders via injection valves connected to the rail.
Typical direct injection, high pressure pumps of the type disclosed in U.S. Pat. No. 7,240,666 have a solenoid valve at the inlet to control flow rate through the pump. The solenoid valve is calibrated to auto-open on every cycle. This allows reduced flow even if the solenoid valve fails (for limp home operations), but does not provide precise control when the valve is operating properly.
With the methodology of the conventional solenoid valves for high pressure pumps, the solenoid valve only assists auto-open for longer flow control.